Electronic thermometers are widely used in the healthcare field for measuring a patient's body temperature. Typical electronic thermometers have a base unit that is held in the palm of a hand and a probe with an elongated shaft connected to the base. The base unit includes a probe well for holding the probe when the thermometer is not in use. Electronic temperature sensors such as thermistors or other temperature sensitive elements are contained within a tip of the probe. When the tip is placed, for example, in a patient's mouth, the tip is heated up by the patient's body and the thermistor measures the temperature of the tip. Electronic components in the base unit receive input from the sensor components to compute the patient's temperature. The temperature is then typically displayed on a visual output device such as a seven segment numerical display device. Typically, electronic thermometers are powered by batteries to make the thermometers portable. Since the thermometers are portable, wall mounts or other holders may be included with the thermometers to provide places to securely store the thermometers.
Some medical-grade electronic thermometers have an anti-theft mechanism for deterring theft. One type of anti-theft mechanism employs a microcontroller with a counter that records the number of uses of the thermometer. When the counter reaches a predetermined number, then the thermometer is disabled. The counter can be reset by placing the thermometer on the wall mount, for example. When the thermometer is placed back on the wall mount, an anti-theft switch in the thermometer is activated, resetting the counter. A conventional anti-theft switch may include a reed switch in communication with the microcontroller. In this type of anti-theft mechanism, the mount includes a magnet having sufficient strength to bring the contact reeds together within the tube of the switch (activating the switch), thereby resetting the counter. Like the true mechanical switch, the reed switch is prone to mechanical wear and failure. Moreover, the reed switch is fragile, as the contact reeds are maintained in a glass vacuum tube. Still further, the magnet used to open the switch typically must have a flux density of at least about 1200 Gauss, which means the magnet is probably bulky and expensive.